Adults with Down syndrome: a comprehensive approach to manage complexity.

BACKGROUND: Down syndrome (DS) is characterised by premature ageing that affects selected organ systems, and persons with this condition can present patterns of co-morbidities and deficits often observed in the older population without DS. However, information on the characteristics of adult persons with DS is limited. The objective of the study is to describe characteristics of adults with DS collected with a standardised, comprehensive assessment instrument. METHODS: Cross-sectional study. Four hundred thirty adults with DS (age range 18/75 years) from three countries (Italy, n = 95; USA, n = 175; and Canada, n = 160). A standardised assessment instrument (interRAI intellectual disability) was used to assess sample characteristics. RESULTS: Mean age ranged from 35.2 (standard deviation 12.0) years in the US sample to 48.8 (standard deviation 9.0) years in the Canadian sample. Most participants in the Italian and US sample were living in private homes, while more than half of those in the Canadian sample were institutionalised. Prevalences of geriatric conditions, including cognitive deficits, disability in the common activities of daily living, symptoms of withdrawal or anhedonia, aggressive behaviour, communication problems, falls and hearing problems were high in the study sample. Gastrointestinal symptoms, skin and dental problems and obesity were also frequently observed. CONCLUSIONS: Adults with DS present with a high level of complexity, which may suggest the need for an approach based on a comprehensive assessment and management that can provide adequate care. Further research is needed to understand better the effectiveness of such an approach in the DS population.

Bone mineral density in adults with Down syndrome.

This study analyzed data of bone mineral density (BMD) from a large cohort of adults with Down syndrome (DS). BMD was found to decrease with age more rapidly in these subjects than in the general population, exposing adults with DS to an increased risk of osteoporosis and bone fracture. INTRODUCTION: Down syndrome (DS) in adulthood presents with a high prevalence of osteoporosis. However, in DS, bone mineral density (BMD) can be underestimated due to short stature. Furthermore, the rate of age-related decline in BMD and its association with gender in DS has been rarely evaluated or compared with the general population. The present study is aimed at assessing the variation of BMD with age and gender in a sample of adults with DS and to compare these data with those of the general population, after adjusting for anthropometric differences. METHODS: Adults with DS, aged 18 or older, were assessed dual-energy-X-ray-absorptiometry (DXA) at the femoral neck and at the lumbar spine. They were compared with the general population enrolled in the National Health and Nutrition Examination Survey (NHANES) 2009-2010 dataset. Bone mineral apparent density (BMAD) was calculated for each individual. RESULTS: DXA was evaluated in 234 subjects with DS (mean age 36.93 ± 11.83 years, ranging from 20 to 69 years; 50.4% females). In the lumbar spine both mean BMD (DS 0.880 ± 0.141 vs. NHANES 1.062 ± 0.167, p < 0.001) and BMAD (DS 0.138 ± 0.020 vs. NHANES 0.152 ± 0.020, p < 0.001) were significantly lower in the DS sample than in the NAHNES cohort. The same trend was observed at the femoral neck in both BMD (DS 0.658 ± 0.128 vs. NHANES 0.835 ± 0.137, p < 0.001) and BMAD (DS 0.151 ± 0.030 vs. NHANES 0.159 ± 0.028, p<0.001). Age was associated with lower femoral neck BMAD in both samples; importantly, this association was significantly stronger in the DS sample. In the lumbar spine region, no significant association between BMAD and age could be observed in both samples. CONCLUSIONS: Adults with DS have lower bone mineral density compared to the general population and they experience a steeper decline with age. Early screening programs are needed in DS population.

Thyroid Function and its Implications in Oxidative Stress Influencing the Pathogenesis of Osteoporosis in Adults with Down Syndrome: A Cohort Study.

People with Down syndrome (DS) show lower bone mass density (BMD) and a higher prevalence of hypothyroidism compared to general population. Furthermore, DS is a well-known high oxidative stress (OS) condition because genes involved in OS map on chromosome 21. Thyroid function too is involved in OS. Since both thyroid function and OS lead to lower BMD and osteoporotic fractures, we have explored correlations among BMD, thyroid hormones, and parameters of OS in DS adults. A total of 105 DS patients (48 males; 21-71 years; mean BMI 28.88±7.12 kg/m(2)) were enrolled in a cohort study, 48 of them undergoing thyroid replacement therapy. We evaluated thyroid function, BMD, and total antioxidant capacity (TAC) in blood plasma. TAC was assayed by H2O2-metmyoglobin system, as source of radicals, and by the chromogenous ABTS, with a latency time (LAG) in the appearance of its cation ABTS+proportional to antioxidant concentration. BMD was evaluated with DEXA, using WHO criteria to classify osteoporosis. Low BMD was found in 83.78% of patients. TSH and LAG did not correlate with BMD. Nevertheless, LAG significantly correlates to Z-scores estimated at the lumbar spine (r(2)=0.558; p=0.03) in hypothyroid patients. Our data show that low TAC could be more associated with reduced BMD rather than TSH itself in DS patients and that the OS could have a role in the pathogenesis of osteoporosis regarding the hypothyroid subgroup.

Unraveling the hidden catalytic activity of vertebrate class IIa histone deacetylases.

Previous findings have suggested that class IIa histone deacetylases (HDACs) (HDAC4, -5, -7, and -9) are inactive on acetylated substrates, thus differing from class I and IIb enzymes. Here, we present evidence supporting this view and demonstrate that class IIa HDACs are very inefficient enzymes on standard substrates. We identified HDAC inhibitors unable to bind recombinant human HDAC4 while showing inhibition in a typical HDAC4 enzymatic assay, suggesting that the observed activity rather reflects the involvement of endogenous copurified class I HDACs. Moreover, an HDAC4 catalytic domain purified from bacteria was 1,000-fold less active than class I HDACs on standard substrates. A catalytic Tyr is conserved in all HDACs except for vertebrate class IIa enzymes where it is replaced by His. Given the high structural conservation of HDAC active sites, we predicted the class IIa His-Nepsilon2 to be too far away to functionally substitute the class I Tyr-OH in catalysis. Consistently, a Tyr-to-His mutation in class I HDACs severely reduced their activity. More importantly, a His-976-Tyr mutation in HDAC4 produced an enzyme with a catalytic efficiency 1,000-fold higher than WT, and this "gain of function phenotype" could be extended to HDAC5 and -7. We also identified trifluoroacetyl-lysine as a class IIa-specific substrate in vitro. Hence, vertebrate class IIa HDACs may have evolved to maintain low basal activities on acetyl-lysines and to efficiently process restricted sets of specific, still undiscovered natural substrates.

Herpes simplex virus glycoprotein D bound to the human receptor HveA.

Herpes simplex virus (HSV) infection requires binding of the viral envelope glycoprotein D (gD) to cell surface receptors. We report the X-ray structures of a soluble, truncated ectodomain of gD both alone and in complex with the ectodomain of its cellular receptor HveA. Two bound anions suggest possible binding sites for another gD receptor, a 3-O-sulfonated heparan sulfate. Unexpectedly, the structures reveal a V-like immunoglobulin (Ig) fold at the core of gD that is closely related to cellular adhesion molecules and flanked by large N- and C-terminal extensions. The receptor binding segment of gD, an N-terminal hairpin, appears conformationally flexible, suggesting that a conformational change accompanying binding might be part of the viral entry mechanism.

Molecular identification of Borrelia valaisiana and HGE-like Ehrlichia in Ixodes ricinus ticks sampled in north-eastern Italy: first report in Veneto region.

PCR amplification was applied to screen the presence of both Borrelia burgdorferi s.l. and Ehrlichia species in pools of field-collected Ixodes ricinus ticks. The specimens so far analysed (n = 55), grouped in 11 pools, were sampled in Feltre area (Veneto region, NE Italy). Five pools proved positive for B. valaisiana (45%) and one of them (9%) was also positive for Ehrlichia, that was further characterised as a HGE-like Ehrlichia. This is the first report of the two bacteria in the Veneto region. The pool positive for both pathogens was used to adjust a multiplex PCR assay, which allowed the detection and identification of both parasites in a single experiment. The advantages offered by this assay, when standardised, will substantially broaden the perspectives of ecological and epidemiological investigations on animal/human Lyme disease and ehrlichiosis, greatly facilitating disease surveillance and control programs.

Structure of a covalently stabilized complex of a human alphabeta T-cell receptor, influenza HA peptide and MHC class II molecule, HLA-DR1.

An alphabeta T-cell receptor (alphabetaTCR)/hemagglutinin (HA) peptide/human leukocyte antigen (HLA)-DR1 complex was stabilized by flexibly linking the HA peptide with the human HA1.7 alphabetaTCR, to increase the local concentration of the interacting proteins once the peptide has been loaded onto the major histocompatibility complex (MHC) molecule. The structure of the complex, determined by X-ray crystallography, has a binding mode similar to that of the human B7 alphabetaTCR on a pMHCI molecule. Twelve of the 15 MHC residues contacted are at the same positions observed earlier in class I MHC/peptide/TCR complexes. One contact, to an MHC loop outside the peptide-binding site, is conserved and specific to pMHCII complexes. TCR gene usage in the response to HA/HLA-DR appears to conserve charged interactions between three lysines of the peptide and acidic residues on the TCR.

Preference of Cd(II) and Zn(II) for the two metal sites in Bacillus cereus beta-lactamase II: A perturbed angular correlation of gamma-rays spectroscopic study.

Cd-substituted forms of the Bacillus cereus metallo-beta-lactamases (BCII) were studied by perturbed angular correlation of gamma-rays (PAC) spectroscopy. At very low [Cd]:[apo-beta-lactamase] ratios, two nuclear quadrupole interactions (NQI) were detected. For [Cd]:[apo-beta-lactamase] ratios between 0.8 and 3.0, two new NQIs appear, and the spectra show that up to 2 cadmium ions can be bound per molecule of apoenzyme. These results show the existence of two interacting Cd-binding sites in BCII. The relative populations of the two NQIs found at low [Cd]:[apo-beta-lactamase] ratios yielded a 1:3 ratio for the microscopic dissociation constants of the two different metal sites (when only one cadmium ion is bound). X-ray diffraction data at pH 7.5 demonstrate that also for Zn(II) two binding sites exist, which may be bridged by a solvent molecule. The measured NQIs could be assigned to the site with three histidines as metal ligands (three-His site) and to the site with histidine, cysteine, and aspartic acid as metal ligands (Cys site), respectively, by PAC measurements on the Cys168Ala mutant enzyme. This assignment shows that cadmium ions preferentially bind to the Cys site. This is in contrast to the preference of Zn(II) in the hybrid Zn(II)Cd(II) enzyme, where an analysis of the corresponding PAC spectrum showed that Cd(II) occupied the Cys site, whereby Zn(II) occupied the site with three histidines. The difference between Zn(II) and Cd(II) in affinity for the two sites is combined with the kinetics of hydrolysis of nitrocefin for different metal ion substitutions (Zn(2)E, ZnE, Cd(2)E, CdE, and ZnCdE) to study the function of the two metal ion binding sites.

Structure of a soluble secreted chemokine inhibitor vCCI (p35) from cowpox virus.

Most poxviruses, including variola, the causative agent of smallpox, express a secreted protein of 35 kDa, vCCI, which binds CC-chemokines with high affinity. This viral protein competes with the host cellular CC-chemokine receptors (CCRs), reducing inflammation and interfering with the host immune response. Such proteins or derivatives may have therapeutic uses as anti-inflammatory agents. We have determined the crystal structure to 1.85-A resolution of vCCI from cowpox virus, the prototype of this poxvirus virulence factor. The molecule is a beta-sandwich of topology not previously described. A patch of conserved residues on the exposed face of a beta-sheet that is strongly negatively charged might have a role in binding of CC-chemokines, which are positively charged.

Crystal structure of the Ebola virus membrane fusion subunit, GP2, from the envelope glycoprotein ectodomain.

We have determined the structure of GP2 from the Ebola virus membrane fusion glycoprotein by X-ray crystallography. The molecule contains a central triple-stranded coiled coil followed by a disulfide-bonded loop homologous to an immunosuppressive sequence in retroviral glycoproteins, which reverses the chain direction and connects to an alpha helix packed antiparallel to the core helices. The structure suggests that fusion peptides near the N termini form disulfide-bonded loops at one end of the molecule and that the C-terminal membrane anchors are at the same end. In this conformation, GP2 could both bridge two membranes and facilitate their apposition to initiate membrane fusion. We also find a heptad irregularity like that in low-pH-induced influenza HA2 and a solvent ion trapped in a coiled coil like that in retroviral TMs.

X-ray structure of the ZnII beta-lactamase from Bacteroides fragilis in an orthorhombic crystal form.

beta-Lactamases are extracellular or periplasmic bacterial enzymes which confer resistance to beta-lactam antibiotics. On the basis of their catalytic mechanisms, they can be divided into two major groups: active-site serine enzymes (classes A, C and D) and the ZnII enzymes (class B). The first crystal structure of a class B enzyme, the metallo-beta-lactamase from Bacillus cereus, has been solved at 2.5 A resolution [Carfi, Pares, Duée, Galleni, Duez, Frère & Dideberg (1995). EMBO J. 14, 4914-4921]. Recently, the crystal structure of the metallo-beta-lactamase from Bacteroides fragilis has been determined in a tetragonal space group [Concha, Rasmussen, Bush & Herzberg (1996). Structure, 4, 823-836]. The structure of the metallo-beta-lactamase from B. fragilis in an orthorhombic crystal form at 2.0 A resolution is reported here. The final crystallographic R is 0.196 for all the 32501 observed reflections in the range 10-2.0 A. The refined model includes 458 residues, 437 water molecules, four zinc and two sodium ions. These structures are discussed with reference to Zn binding and activity. A catalytic mechanism is proposed which is coherent with metallo-beta-lactamases being active with either one Zn ion (as in Aeromonas hydrophila) or two Zn ions (as in B. fragilis) bound to the protein.

1.85 A resolution structure of the zinc (II) beta-lactamase from Bacillus cereus.

Class B beta-lactamases are wide spectrum enzymes which require bivalent metal ions for activity. The structure of the class B zinc-ion-dependent beta-lactamase from Bacillus cereus (BCII) has been refined at 1.85 A resolution using data collected on cryocooled crystals (100 K). The enzyme from B. cereus has a molecular mass of 24 946 Da and is folded into a beta-sandwich structure with helices on the external faces. The active site is located in a groove running between the two beta-sheets [Carfi et al. (1995). EMBO J. 14, 4914-4921]. The 100 K high-resolution BCII structure shows one fully and one partially occupied zinc sites. The zinc ion in the fully occupied site (the catalytic zinc) is coordinated by three histidines and one water molecule. The second zinc ion is at 3.7 A from the first one and is coordinated by one histidine, one cysteine, one aspartate and one unknown molecule (most likely a carbonate ion). In the B. cereus zinc beta-lactamase the affinity for the second metal-ion is low at the pH of crystallization (Kd = 25 mM, 293 K; [Baldwin et al. (1978). Biochem. J. 175, 441-447] and the dissociation constant of the second zinc ion was thus apparently decreased at the cryogenic temperature. In addition, the structure of the apo enzyme was determined at 2.5 A resolution. The removal of the zinc ion by chelating agents causes small changes in the active-site environment.

Purification, crystallization and preliminary X-ray analysis of Bacteroides fragilis Zn2+ beta-lactamase.

The Zn(2+) beta-lactamase from Bacteroides fragilis (E.C. 3.5.2.6) was overexpressed in Escherichia coli using an isopropylthiogalactoside-inducible T7 RNA polymerase expression system. Crystallization trials by the hanging-drop vapour-diffusion method have yielded two different crystal forms from two slightly different conditions. Crystals of form I belong to the monoclinic space group C2 with unit-cell dimensions a = 56.03, b = 43.98, c = 105.32 A, beta = 112 degrees and diffracted only up to 4.0 A. Crystals of form II are orthorhombic, space group P2(1)2(1)2(1) with unit-cell dimensions a = 48.10, b = 98.05, c = 111.76 A, diffract to at least 2.0 A and are suitable for high-resolution structural analysis.

The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold.

The 3-D structure of Bacillus cereus (569/H/9) beta-lactamase (EC 3.5.2.6), which catalyses the hydrolysis of nearly all beta-lactams, has been solved at 2.5 A resolution by the multiple isomorphous replacement method, with density modification and phase combination, from crystals of the native protein and of a specially designed mutant (T97C). The current model includes 212 of the 227 amino acid residues, the zinc ion and 10 water molecules. The protein is folded into a beta beta sandwich with helices on each external face. To our knowledge, this fold has never been observed. An approximate internal molecular symmetry is found, with a 2-fold axis passing roughly through the zinc ion and suggesting a possible gene duplication. The active site is located at one edge of the beta beta sandwich and near the N-terminal end of a helix. The zinc ion is coordinated by three histidine residues (86, 88 and 149) and a water molecule. A sequence comparison of the relevant metallo-beta-lactamases, based on this protein structure, highlights a few well-conserved amino acid residues. The structure shows that most of these residues are in the active site. Among these, aspartic acid 90 and histidine 210 participate in a proposed catalytic mechanism for beta-lactam hydrolysis.